EP0375202 describes an oxychlorination catalyst composition comprising a mixture of metallic chlorides carried on a support, wherein said mixture consists essentially of a mixture of copper chloride, magnesium chloride, and potassium chloride. It also describes the oxychlorination of ethylene to 1,2-dichloroethane using such a catalyst composition.
DD 90127 relates to a method for producing 1,2-dichloroethane by oxychlorination of ethylene with hydrogen chloride and air. As catalysts according to the invention, mixtures are used which contain copper (II)-chloride as the principal component and as promoters contain chlorides of the metals silver, magnesium, calcium, potassium, cerium and manganese, applied to an inert support. The catalysts are composed of 6 to 10 wt. % of the active catalyst components and 94 to 90 wt. % of the inert support.
RU 2148432 relates to catalytic chemistry and in particular to catalysts for the synthesis of dichloroethane by oxychlorination of ethylene. The method described for preparation of a catalyst for oxychlorination of ethylene to 1,2-dichloroethane includes application of a copper compound as an active component to an aluminum oxide carrier containing a metal ion Me2+ and/or Me3+ in the aluminum oxide with a ratio of Al3+ to Me2± and/or Me3+ in the range from 200:1 to 20:1, with subsequent drying at a temperature ensuring complete crystallization of the active component over a period of less than 30 min. Application of the active component to the carrier and drying are carried out in a controlled-speed rotary drum fitted with a device for introducing an impregnating solution and a heating element for performing the drying.
EP 0582165 relates to catalyst compositions for oxychlorination of ethylene to produce 1,2-dichloroethane. The catalysts comprise copper chloride, at least one alkali metal, at least one rare earth metal, and at least one Group IIA metal on a high surface area support for fluid bed applications or on a high or low surface area support for fixed bed applications. The catalyst compositions are prepared by depositing the metals on a support. The use of the catalyst compositions of the invention in the oxychlorination of ethylene to EDC results in high percent ethylene efficiency, high EDC product purity and high percent HCl conversion without exhibiting catalyst stickiness. A process for oxychlorination of ethylene to produce 1,2-dichloroethane is also disclosed. The process relies on contacting a mixture of ethylene, oxygen or oxygen containing gas and hydrogen chloride with a fixed or fluidized catalyst composition in a reaction zone and recovering 1,2-dichloroethane from the effluents of the reaction zone.
The most commonly used process for the production of 1,2-dichloroethane is the oxychlorination of ethylene. In this process ethylene is converted with HCl and oxygen (or an oxygen containing gas) to form 1,2-dichloroethane and water. In the course of the years both fixed and fluidized bed process variants have been developed and are currently in use.
The by-products formed in the oxychlorination process are carbon oxides (CO+CO2) and chlorinated hydrocarbons. Among these chlorinated by-products 1,1,2-trichloroethane, chloral, ethylchloride, chloroform and carbon tetrachloride are the most common. All by-products lead to a loss in ethylene efficiency and have to be minimized. The chlorinated by-products also need to be incinerated and hence produce further costs.
The catalysts used in oxychlorination processes contain copper chloride as an active ingredient. In order to improve the activity, selectivity and/or the operability, further promoters are introduced into the catalyst formulation. Among the most commonly used are magnesium chloride, potassium chloride, cesium chloride and/or rare earth chlorides.
The active copper species as well as the promoters are usually deposited on a high surface support like kieselguhr, clay, fuller's earth, silica or alumina. In general the copper and the promoters are impregnated onto the support by means of a solution containing all the metals in form of their chlorides. In some cases a co-precipitation of the ingredients with the support is carried out.
In the meantime fluidized bed oxychlorination processes became favored over fixed bed processes due to better economics. Commercial fluidized bed reactors are usually operated with an HCl conversion of 99.5 to 99.8%. The 1,2-dichloroethane selectivity typically lies between 96-97.5%.
The supports used for the production of fluidized bed oxychlorination catalysts are mostly fluidizable gamma alumina with a mean particle size of 30-80 μm and a BET surface area of 120-220 m2/g.
The copper content of fluidized bed oxychlorination catalysts typically lies between 3-17 wt. %. Most fluidized bed processes use catalysts with a copper content of 3-6 wt. %.
In fluidized bed oxychlorination a phenomenon called “catalyst sticking” or “stickiness” can occur under certain conditions. “Sticky Catalyst” results in the agglomeration of catalyst particles resulting often in the collapse of the fluidized bed and/or the plugging of the cyclones. As a consequence severe catalyst carry-over can take place and the reactor is no longer operable. Such a sticking episode causes significant economic damage to a production plant and has to be avoided by all means. Stickiness in oxychlorination can be caused either by inappropriate operational conditions or by the properties of the catalyst itself. The following operational conditions favor stickiness:
i) high Cl/C ratio
ii) low O/C ratio
HO low operation temperature.
Hence a fluidized bed oxychlorination catalyst must have a high resistance towards stickiness.